Nemerteans
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Nemertean. Photo: George Washington University |
Habitat
Most of the common shallow-water species live beneath shells, stones or in algae. Some live in mud and sand, and have semi-permanent burrows lined with mucus or cellophane-like tubes. A few species live in deep water. Some live in symbiotic (mutually beneficial) relationships with crabs, bivalve molluscs or tunicates.
Physiology
Most nemerteans look like big flatworms, but much larger, longer and thicker-bodied. Some have the appearance of being segmented, but are not. Most species are less than 20 cm in length, and some just a few millimetres. Others may measure several metres or more. One European species (Lineus longissimus), which lives coiled under large rocks, is reported to be up to 30 metres in length!
Most nemerteans are pale in colour. Others have bright patterns of yellow, orange, red and green. The deep water species that live below depths to which light penetrates, are bright red, orange or yellow - but these colours appear black at such depths.
Feeding
Nemerteans use their proboscis to spear, hold and poison their food.
